1. Field of the Invention
This invention relates to a color display device, more particularly to a color display device utilizing particle polarization.
2. Description of the Related Art
U.S. Pat. No. 7,492,505 discloses an electrophoretic display containing an array of electrophoretic cells. Referring to FIGS. 1 and 2, each of the electrophoretic cells includes a top layer 10 containing a top electrode 101, a bottom layer 20 containing a bottom electrode 201 and at least one in-plane electrode 202, and an electrophoretic composition 30 filled therein. The electrophoretic composition 30 contains a dielectric solvent 301 and a group of charged pigment particles 302 that carry the same charge polarity.
Referring to FIG. 1, when there is no voltage difference between the in-plane electrodes 202 (that is, the display is under an off state), the charged pigment particles 302 are dispersed randomly in the dielectric solvent 301, and the color of the electrophoretic display is provided through the group of charged pigment particles 302.
Referring to FIG. 2, when the in-plane electrodes 202 are set at low voltage, the charged pigment particles 302 migrate to sides of the cell, and the color of the electrophoretic display is provided through the dielectric solvent 301 or the background (best shown in the right portion of FIG. 2). When the voltage of the top electrode 101 is set low and the voltage of the bottom electrode 201 is set high, the charged pigment particles 302 migrate to the top electrode 101, and the color of the electrophoretic display is provided through the charged pigment particles 302 (best shown in the left portion of FIG. 2). In this patent, since the in-plane electrodes 202 are necessary, the manufacturing cost is relatively high, and the difficulty in driving the electrophoretic display is also increased.
U.S. Patent Application Publication No. 2009/0135131 discloses a display utilizing a different driving mode. Referring to FIGS. 3 and 4, the display includes first and second substrates 50, 70, first and second electrodes 60, 80 attached to inner faces of the first and second substrates 50, 70, respectively, and a mixed solution 90 disposed between the first and second electrodes 60, 80. The mixed solution 90 contains a solution 901 and a group of neutral micro-particles 902 dispersed in the solution 901.
Referring to FIG. 3, when the display is under an off state, the neutral micro-particles 902 are dispersed randomly in the solution 901. Referring to FIG. 4, when the display is under an on state, the neutral micro-particles 902 are electrically polarized to form a plurality of strings of the neutral micro-particles 902. In an embodiment shown in FIG. 2 of the U.S. patent publication, the display includes a plurality of first neutral micro-particles, a plurality of second neutral micro-particles, and a plurality of third neutral micro-particles. The first neutral micro-particles may be red, the second neutral micro-particles may be green, and the third neutral micro-particles may be blue. The first neutral micro-particles, the second neutral micro-particles, and the third neutral micro-particles have a first driving frequency, a second driving frequency, and a third driving frequency, respectively. Therefore, the first neutral micro-particles, the second neutral micro-particles, and the third neutral micro-particles will be polarized under driving voltages of different frequencies.